Effect of calmodulin antagonists on contraction and45Ca movements in rat aorta

To study the selectivity of calmodulin antagonists it was assumed that they should inhibit noradrenaline (NA)- and K+-induced contractions similarly without an accompanying inhibition of45Ca uptake. Therefore, in isolated rat aorta the effects of W-7, calmidazolium and trifluoperazine on contraction and45uptake elicited by K+and NA were investigated. Calmidazolium (10-5-10-4mol/l) elicited an incomplete inhibition of K+- and NA-induced contraction and45Ca uptake. Trifluoperazine inhibited the NA-induced contractions at lower concentrations (10-6-10-4mol/l). The K+- and NA-induced45Ca uptake was blocked by trifluoperazine (10-5mol/l). W-7 (10-5-10-4mol/l) inhibited the K+- and NA-induced45Ca uptake. In conclusion, the results indicate that calmidazolium and trifluoperazine are hardly useful as calmodulin antagonists because of their additional properties, whereas W-7 seems to be the least unspecific of the calmodulin antagonists studies.